This invention relates to a method and apparatus for chemically and/or physically treating a dust cloud. The method involves generating a dust cloud from a gas and solid particles, passing the dust cloud through a reaction zone and subsequently separating the components and at least partially reintroducing the gas and/or the solid particles into the dust cloud.
It is known that chemical and/or physical processes, particularly thermal treatments may be performed on matter forming a dust cloud which is formed of a gas containing one or several gaseous materials and solid particles formed of one or several solid substances. The dust cloud is in motion and passes through a reaction zone in which, for example, chemical reactions, heat exchange processes, adsorption processes, or classification of solids take place. The gas always serves as the carrier means for the solid particles; it may, nevertheless, participate in the treatment to which the dust cloud is submitted. After the dust cloud has passed through the reaction zone by means of appropriate apparatuses such as dust removing chambers or cyclones, it is separated to its components. Gas and solid particles leave, along different paths, the apparatuses which serve for the separation of the dust cloud, and are, dependent upon the type and course of the treatment, further utilized, or are disposed of in part as non-usuable reaction products or are reintroduced into the dust cloud. As a rule, the process does not evolve quantitatively during a single passage of the dust cloud through the reaction zone; thus, at least a partial recirculation of the gas and/or the solid particles is necessary. The dust cloud is generated by mixing a gas stream with solid particles of appropriate grain size. In a dust cloud the gas and all solid particles move continuously with an approximately identical speed from location A to location B, while in a layer of turbulance a large part of the solid particles is in a location-bound motion (floating state) and thus only the gas and some of the solid particles reach location B from location A.
It is further known to remove the solid particles (after the separation of the dust cloud) from the separators by means of oscillating flaps, augers, compartmented wheel gates or the like in a mechanical manner and to occasionally reintroduce them into the dust cloud. All these conveying devices have, however, the disadvantage that they include movable components exposed to wear which increases the likelihood of breakdown and involves elevated energy and maintenance costs.